Device and method for producing dialysate

ABSTRACT

The present invention relates to a device and to a method for producing dialysate, wherein the device comprises a first part and a second part designed as a circuit, wherein the first part comprises a water connection or a water container and the primary side of a filter, wherein the filter is designed to produce purified water from the water by forward osmosis, and wherein the second part comprises the secondary side of the filter, a reservoir, a filtrate line which leads from the secondary side of the filter to the reservoir, and a return line leading from the reservoir to the secondary side of the filter, wherein an electrodialysis unit comprising a diluate chamber and a concentrate chamber is further provided, wherein the concentrate chamber is fluidically connected to the secondary side of the filter.

The present invention relates to a device and to a method for producing dialysate.

It is known from the prior art to supply dialysis machines with ready-to-use dialysate, i.e. with ready-to-use dialysis solution, e.g. from a line system which is connected to a central apparatus for producing the dialysate and is generally designed to supply a plurality of dialysis machines with dialysate.

Furthermore, it is known from the prior art to produce the dialysate on the dialysis machine, i.e. in a decentralized manner. For this purpose, an RO system (RO=reverse osmosis) may be used for producing ultrapure water, which system is part of the dialysis machine or may be constructed as a separate unit. The ultrapure water is mixed with one or more concentrates in the dialysis machine in order to obtain a ready-to-use dialysate for treating the patient. Producing ultrapure water by means of the RO process has a drawback in that the process requires high pressure in the range of from 6 to 15 bar, which is accordingly energy-intensive.

The problem addressed by the present invention is to provide a device and a method by means of which it is possible to produce dialysate in an energy-efficient manner.

This problem is solved by a device having the features of claim 1 and by a method having the features of claim 15.

Accordingly, it is provided that the device comprises a first part and a second part designed as a circuit, wherein the first part comprises a water connection or a water container and the primary side of a filter, wherein the filter is designed to produce purified water from the water by forward osmosis, and wherein the second part comprises the secondary side of the filter, a reservoir, a filtrate line which leads from the secondary side of the filter to the reservoir, and a return line leading from the reservoir to the secondary side of the filter, wherein an electrodialysis unit comprising a diluate chamber and a concentrate chamber is further provided, wherein the concentrate chamber is fluidically connected to the secondary side of the filter.

The combination with the electrodialysis provided according to the invention to increase the (volumetric) concentration of the freely movable electrolytes by applying an electrical field results in an increased concentration of the electrolytes on the filter and therefore in an increase in the osmotic pressure.

It is preferably provided that raw water or tap water is obtained from the water container or water connection.

One or more concentrates may be contained in the reservoir, from which a dialysate can be produced by dilution or dissolution in permeate.

In the context of the present invention, the term “dialysate” covers both a ready-to-use dialysis solution and one or more components thereof.

The present invention is therefore based on the concept of using the differing electrolyte concentration between raw water and dialysate/concentrate and the associated osmotic pressure in order to produce dialysate by means of a suitable forward-osmosis membrane of the filter. Forward osmosis is also referred to as FO in the following for short. In order to increase the osmolarity on the filtrate side of the filter, the electrodialysis unit is used, the concentrate chamber(s) of which is/are fluidically connected to the secondary side of the filter.

For producing dialysate, the permeate is mixed with one or more concentrates after production until a physiological electrolyte concentration or the desired electrolyte concentration is reached. Preferably, at least one of the concentrates is contained in the reservoir. It is conceivable for at least one concentrate (or all the concentrates) to be supplied to the second part of the device via a concentrate line.

The substance concentration of electrolytes (and therefore the conductivity as a sum parameter for the electrolyte concentration) is considerably higher in the dialysate or dialysate concentrate than in tap water. The electrical conductivity of drinking water is (according to the German Drinking Water Ordinance) max. 2.79 mS/cm, and the electrical conductivity of dialysate is usually 12 to 16 mS/cm. This difference (which does not restrict the invention) in the electrolyte concentration results in an osmotic pressure gradient, which is utilized according to the invention for the process of producing dialysate by FO. An increase in the osmolarity on the secondary side of the membrane is achieved by the electrodialysis unit.

The water, which is preferably tap water, is preferably heated to produce dialysate or dialysate concentrate (preferably to 37° C.). If this takes place right at the start of the process, the efficiency of the FO process is increased, since the osmotic pressure gradient is directly temperature-dependent.

An essential element of the invention is the use of forward osmosis for preparing dialysate. This preparation can be carried out by using used dialysate or raw water. The use of raw water, e.g. from the household supply, is preferred. The FO membrane is therefore preferably also a sterile barrier, such that good home dialysis is possible both for HD (hemodialysis) and for PD (peritoneal dialysis) from concentrates (dry, liquid, etc.).

The concentrate or dialysate is preferably guided in the circuit on the secondary side until the desired final concentration, final conductivity, etc. is achieved.

The second part of the device is a circuit. In a preferred configuration of the invention, the first part of the device is also designed as a circuit, i.e. the water is guided past the primary side of the filter in the circuit and the dialysate or dialysate concentrate is guided past the secondary side of the filter in the circuit. A component of the circuit is the electrodialysis unit.

Preferably, the diluate chamber of the electrodialysis unit is fluidically connected to the reservoir.

It is also conceivable for a conductivity-measuring cell or a concentration-measuring cell to be arranged upstream of the diluate chamber in the flow direction of the dialysate. In the context of the invention, these are understood to be measuring apparatuses by means of which the conductivity and/or concentration can be deduced.

It is conceivable for a pump to be arranged between the conductivity-measuring cell or concentration-measuring cell and the electrodialysis unit.

In another configuration of the invention, a conductivity-measuring cell or a concentration-measuring cell is arranged downstream of the diluate chamber in the flow direction of the dialysate.

The conductivity-measuring cell or concentration-measuring cell may be arranged between the diluate chamber and the reservoir.

It is also conceivable for the conductivity-measuring cell or concentration-measuring cell to be arranged between the reservoir and the filter. It is conceivable here for a pump to be arranged between the conductivity-measuring cell or concentration-measuring cell and the filter. The pump can also be arranged at a different point in the secondary circuit, for example also upstream of the conductivity-measuring cell or concentration-measuring cell.

In another configuration of the invention, a line portion is provided which leads from the concentrate chamber to the return line, which in turn leads from the reservoir to the secondary side of the filter 4.

A dialysate concentrate may be contained in the reservoir, which is preferably formed as a bag or as another container.

A plurality of reservoirs may be provided and a valve assembly may be provided which is designed to alternately switch a plurality of reservoirs into a fluidic connection to the second part of the device.

A bicarbonate concentrate and/or an acidic concentrate which is configured to produce dialysate may be contained in the reservoir.

It is also conceivable for a plurality of compartments to be provided in the reservoir, in each of which one or more concentrates are contained.

The concentrate may be contained in the reservoir in the form of a powder, granulate, slurry or in liquid form.

The concentrate may also be supplied via separate lines.

The present invention also relates to a method for producing dialysate using a device according to any of claims 1 to 14, wherein water is supplied to the primary side of the filter, the permeate is supplied to the secondary side by forward osmosis, and a dialysate concentrate that is mixed with the permeate is supplied to the secondary side of the filter from the reservoir and/or from another source. The concentration of the dialysate present on the secondary side of the filter is increased by means of electrodialysis.

The dialysate or dialysate concentrate may be conveyed in the circuit on the secondary side of the filter until the conductivity and/or a concentration or another parameter representative of these parameters corresponds to a target value or is in a target-value range.

A plurality of reservoirs may be provided in the second part of the device, one reservoir being filled with the dialysate or the dialysate concentrate and the other reservoir being emptied for use in a dialysis machine.

According to the invention, it is also conceivable for a physiologically acceptable substance, in particular glucose, or a substance that is to be precipitated before use as dialysate, in particular magnetic iron nanoparticles, to be added in order to further increase the osmotic pressure on the secondary side of the filter.

Using a device according to the present invention, one or, even better, two small chambers or reservoirs can be filled with ready-to-use dialysate, for example, such that a chamber is always available for removing dialysate. This device is also referred to as “micro-batch”. However, a large supply of, for example, 2-5 liters (typical for PD) or 70-100 liters (typical for HD) may also be provided, for example in a reservoir, in particular a bag. A device or method of this kind is also referred to as “macro-batch”.

An FO process uses the osmotic pressure gradient for filtering water, preferably tap water. The energy-intensive production of permeate by RO does not take place according to the invention and dialysate or dialysate concentrate is directly produced. Since the preparation process preferably takes place immediately before the use of the fluid, i.e. there is no tube network therebetween, the complexity of maintaining the required hygiene is reduced. New options for portability are also conceivable due to continuous miniaturization. In addition, the process is considerably quieter than the RO system with the associated pump for pressure generation.

The reservoir is preferably a bag, which comprises flexible walls in part or in full. A reservoir which comprises rigid walls in part or in full, such as a cartridge, is also conceivable and is covered by the invention. In a preferred configuration of the invention, the reservoir comprises connection means for fluidic connection to a dialysis machine.

It is preferable for a plurality of reservoirs, preferably two reservoirs, to be provided and for a valve assembly to be provided which is designed to alternately switch the reservoirs to the second circuit. The reservoir that is not connected to the second circuit can be removed and used during the dialysis. Simultaneously, the other reservoir is filled with the ready-to-use dialysate or dialysate concentrate.

Said means of the reservoir may be a connector or a tube or a connection for a tube or other means which can establish a fluidic connection between the interior of the reservoir and a dialysis machine. The reservoir, which is preferably formed as a bag, can preferably be directly fixed to a mating part on a dialysis machine by means of a connector. It is also conceivable for the reservoir to have a tube or an adapter for a tube, by means of which the ready-to-use dialysate or dialysate concentrate can be used, for example in the field of peritoneal dialysis.

The concentrate that is preferably contained in the reservoir may for example be a bicarbonate concentrate and/or an acidic concentrate which is configured to produce dialysate.

The concentrate may be contained in the reservoir e.g. in the form of a powder, granulate, slurry or in liquid form.

A pump is preferably arranged in the first part and/or the second part of the device, which is also referred to as the “second circuit”. If the pump is located in the first part, a sufficiently high transmembrane pressure can be generated by means of the pump in order to increase the permeate flow on the primary side of the filter. The pump on the secondary side has the advantage that the dialysate or the dialysate concentrate can be repeatedly guided past the filter membrane until the desired concentration or conductivity, etc., is achieved. In addition, the pump can be used on the secondary side for maintaining a high dialysate flow, e.g. during priming.

In order to detect the end time of the production of the dialysate or dialysate concentrate, a sensor, preferably a conductivity-measuring cell, can be arranged in the second circuit. If this has a measured value that is within a target-value range, the production of the dialysate or dialysate concentrate can be considered to have ended and the reservoir can be removed for use in dialysis treatment. For example, the reservoir can also be designed to have a fixed volume and the sensor can be formed by a fill-level probe. It is likewise conceivable for a gravimetric end-time determination to be carried out.

It is conceivable for a concentrate line, which in turn is connected to a reservoir for dialysate concentrate, to open into the second circuit, such that another concentrate can be introduced into the second circuit by means of the concentrate line. This is useful when the reservoir does not contain all the required concentrates, but only some of said concentrates.

The reservoir can comprise precisely one compartment in which one or more concentrates are contained, which are dissolved by means of the permeate in the context of the present invention. It is also conceivable for the reservoir to comprise a plurality of compartments, in each of which one or more concentrates are contained. It is possible here for the compartments to be arranged and formed such that they are open in a phased manner, such that there are particular osmolarities in a phased manner.

The present invention also relates to a method for producing a dialysate using a device according to any of claims 1 to 14, wherein water, preferably tap water, is supplied to the primary side of the filter, wherein the permeate is supplied to the secondary side by forward osmosis, and wherein a dialysate or dialysate concentrate that is mixed with the permeate is supplied to the secondary side of the filter from the reservoir and/or from another source, and the concentration of the dialysate is increased on the secondary side by electrodialysis.

It is preferably provided that the dialysate or dialysate concentrate is conveyed in the circuit on the secondary side until the conductivity and/or a concentration or another parameter correlated therewith corresponds to a target value or is in a target-value range.

It is conceivable, if there is a plurality of reservoirs, for one reservoir to be filled with the dialysate or the dialysate concentrate in the second circuit and for the other reservoir to be emptied for use in a dialysis machine, i.e. as part of dialysis treatment.

It is advantageous for a physiologically acceptable substance, in particular glucose, or a substance that is to be precipitated before use as dialysis solution, in particular magnetic iron nanoparticles, to be added in order to increase the osmotic pressure on the secondary side of the filter.

It should be noted at this point that the terms “a”, “an” and “one” do not necessarily refer to exactly one of the elements, even though this constitutes a possible configuration, but instead they can also denote a plurality of said elements. Likewise, the use of the plural also includes the presence of the element in question in the singular and, vice versa, the singular also includes a plurality of the elements in question.

Other details and advantages of the invention are explained in greater detail with reference to an embodiment shown in the drawings, in which:

FIG. 1 is a schematic flow chart of a device according to the invention in a first embodiment,

FIG. 2 is a schematic flow chart of a device according to the invention in a second embodiment,

FIG. 3 is a schematic flow chart of a device according to the invention in a third embodiment, and

FIG. 4 is a schematic flow chart of a device according to the invention in a fourth embodiment.

Reference sign 1 in FIG. 1 shows a heat exchanger on the raw-water inlet. Heating the raw water supplied to the filter 4 increases the effectiveness of the osmosis process. Reference sign 2 denotes the raw-water inlet chamber, which comprises a vent and/or a level sensor.

As is clear from FIG. 1 , the device comprises a first part in the form of a raw-water circuit and a second part in the form of the mixing circuit.

Reference sign 3 denotes the circulation pump in the raw-water circuit, i.e. in the first circuit according to the invention. Reference sign 4 denotes the FO filter, and reference sign 5 denotes the conductivity/temperature measuring cell for raw water and “back-flow” monitoring. Reference sign 6 denotes the raw-water circulation valve and reference sign 7 denotes the flush valve for flushing the filter 4.

The raw-water circulation valve 6 may be designed to set and/or regulate the transmembrane pressure. If the transmembrane pressure is too high or too low, the raw-water circulation valve is opened or closed in full or in part.

Reference sign 8 denotes the discharge, reference sign 9 denotes an A concentrate pump (dialysis concentrate/acid concentrate) (A concentrate can also be added later) and reference sign 10 denotes a B concentrate pump (dialysis concentrate/bicarbonate concentrate).

Reference sign 17 denotes a degassing device and reference sign 15 denotes a device for heating the water supplied to the primary side of the filter 4.

Reference sign 13 denotes the circulation pump in the mixing circuit, i.e. in the second circuit according to the invention. Reference sign 14 denotes a concentrate bag, which is used as a collection chamber and can be configured to comprise a vent and level sensor (the filtrate is accumulated here). Preferably, two parallel collection chambers, preferably concentrate bags, are provided. However, rigid reservoirs may also be provided. Therefore, one chamber can always be filled with dialysate and the other chamber can always be emptied and used as part of the dialysis treatment.

Reference sign 16 is a conductivity/temperature measuring cell for monitoring the quality and composition of the dialysate (filtrate+bicarbonate mixing ratio or filtrate+bicarbonate+acid concentrate mixing ratio). Alternatively, a second measuring cell can be used for readjusting the B concentrate. The measuring cell 16 is arranged upstream of the pump 13.

A heat exchanger 1, which is arranged upstream of the filter 4, is provided for heating the raw water. Raw water to be heated flows through the heat exchanger on one side and the dialysate present on the secondary side flows through said heat exchanger on the other side, which dialysate heats the raw water in the heat exchanger 1. The heat exchanger may alternatively also be provided between the flush valve 7 and the discharge 8, such that the heat of the water supplied to the discharge can be transferred to the raw water to be heated.

The pump 13 conveys the dialysate in the electrodialysis unit 18, which comprises at least one anion exchanger membrane and at least one cation exchanger membrane between two electrodes. A stack of alternating anion and cation exchanger membranes is usually provided. Each pair of ion exchanger membranes or a pair formed by an ion exchanger membrane and an electrode form a separate chamber. When an electrical direct current is applied to the electrodes, salts are enriched in the concentrate chamber(s) and low-salt solutions are formed in the diluate chamber(s).

The pump 13 conveys the dialysate of the secondary circuit into the electrodialysis unit 18, which, in the simplified embodiment shown here, consists of a central diluate chamber D and two concentrate chambers K1, K2 at the sides. From the concentrate chambers K1, K2, the concentrate reaches the secondary side of the filter 4. This takes place via a line L1, in which the shut-off valve 19 is positioned and which opens from the chambers K1, K2 into the return line R, which in turn fluidically connects the bag 14 etc. to the secondary side of the filter 4.

The shut-off valve 21 is positioned downstream of the bag 14.

A line L2, which leads to the bag 14, extends from the diluate chamber D of the electrodialysis unit 18. The shut-off valve 20 is positioned in this line and a conductivity-measuring cell 22 is positioned downstream of said valve.

The sequence for producing dialysate or dialysate concentrate is configured as follows, by way of example:

0. (Initial Preparation)

The FO filter 4 is filled with raw water (tap water) on the raw-water side, i.e. on the side of the first circuit.

The FO filter 4 is filled with physiological solution on the filtrate side or raw water or permeate (=filtrate) is pushed onto the filtrate side by slight overpressure on the raw-water side.

1. Addition of Concentrate to the Mixing Circuit

Example: Volume in the mixing circuit: 800 ml (400 ml in the filter/400 ml in the circuit)

Addition of concentrate: 11.4 ml A concentrate and 14 ml B concentrate.

2. Addition of Permeate to the Mixing Circuit

Permeate (filtrate) flows through the FO membrane until the correct mixing ratio is obtained. This is relevant for the osmotic pressure and therefore for the permeate flow through the membrane.

Monitoring of the mixing ratio (target Na concentration in the dialysate typically 138 mmol/L) by measuring the dialysate conductivity (typically 12 to 16 mS/cm).

3. Removal of the Prepared Dialysate

New cycle starts with the addition of concentrate (1→2→3)

The voltage of the electrodes (anode, cathode) of the electrodialysis unit 18 can be set such that the conductivity-measuring cells 22 and 16 each measure the desired conductivities.

It is, however, also conceivable for the conductivity to differ from the expected value for the ready-mixed dialysate to the end during the process of mixing a filling of the bag 14.

As part of producing dialysate, a cycle is started, i.e. concentrate (A and/or B) is supplied, by 9 and/or 10. The concentrate diluted by the filter 4 is repeatedly concentrated by the electrodialysis unit 18 without the correct, relative mixing ratio of the electrolytes for dialysate necessarily being maintained in the return via the valve 19 in the process.

At the end of the process, however, the entire volume of the circuit comprising the components 4, 18 and 14 ends up in the reservoir 14, as a result of which all the electrolytes from the circuit comprising the components 18, 19 and 4 are also conveyed into the reservoir 14 and the composition is finally correct.

In this case, it is particularly advantageous for a conductivity measuring cell for sampling to be arranged upstream or downstream of the valve 21, which is arranged downstream of the reservoir 14, and downstream of the reservoir 14, and specifically in addition to or instead of the conductivity measuring cell 22 according to FIG. 1 . An embodiment of this kind is shown in FIG. 2 . In this embodiment, the conductivity measuring cell 22 is arranged between the valve 21 and a pump 13, which is arranged in the return line R upstream of the opening of the line L1 into the return line R. The pump 24, which is arranged at the position of the pump 13 in FIG. 1 , is likewise present in the secondary circuit.

In the embodiment according to FIG. 2 , a degassing device 25 is arranged upstream of the filter 4 in the raw-water circuit, from which device a degassing line E, in which a shut-off valve 23 is positioned, leads to the raw-water inlet chamber 2. The degassing has the advantage that no air bubbles can get into the filter 4, and therefore the effectiveness of the FO process is further increased.

Moreover, with regard to the embodiment according to FIG. 2 , reference is made to the embodiment according FIG. 1 .

Other components are only shown by way of example. Therefore, for example, instead of the pump 13, a pump could also be provided between 14 and 21 and another pump could be provided between 18 and 19.

FIG. 3 shows an embodiment that largely corresponds to FIG. 2 , with the difference that the pump 24 upstream of the electrodialysis unit 18 is omitted and the pump 13 is not downstream of the reservoir 14 in the flow direction as in FIG. 2 , but instead is arranged downstream of the opening of the line L1 into the return line R.

FIG. 4 corresponds to the embodiment according to FIG. 3 , with the difference that the heat exchanger 1 for heating the raw water inlet into the container 2 is heated by the fluid that is discharged from the container 2 into the discharge 8. As is clear from FIG. 4 , the line leading to the heat exchanger 1 can branch off e.g. downstream of the flush valve 7.

It is noted that all the components of the embodiments are optional except for the core components (4, 14, 18) and are shown by way of example in order to illustrate a possible application.

Returning the used dialysate to chamber 2 would also be conceivable in order to carry out reprocessing according to the patent DE102018105120 and to thus save energy and water.

It is likewise conceivable to assist the FO process in the filter 4 with an additional, hydraulic pressure or negative pressure of a pump.

The entire process can also be configured as a continuous process with the continuous addition of concentrate, production of permeate and removal of dialysate.

It is also possible to install a second collection chamber or reservoir, and preferably bags, which chamber or reservoir is filled alternately to the first chamber. Therefore, dialysate can be removed from one chamber while the other chamber is filled. This ensures that dialysate can be produced virtually continuously.

The following can preferably be mentioned as options for increasing the osmolarity on the product side of the filter 4:

In order to increase the osmotic gradient between the tap water and dialysate and therefore the performance of the osmosis process, it is possible, on the product side, i.e. in the second circuit:

a. To add a physiologically acceptable additive. Glucose would be a possible substance here, and is currently already contained in HD dialysate in concentrations of up to 1 g/l.

b. To add a substance which does not remain in the dialysate, but instead is physically or chemically precipitated beforehand (or is retained by the dialyzer). Magnetic iron nanoparticles would be suitable for this purpose. The particles are added upstream of the filter and are precipitated downstream of the filter by means of a magnetic field.

Returning the used dialysate to the chamber 2 would also be conceivable in order to carry out reprocessing and to thus save energy and water.

It is likewise conceivable to assist the FO process in the filter 4 with an additional, hydraulic pressure or negative pressure of a pump.

The following can be mentioned as a supplementary idea: testing the forward-osmosis filter 4 in operation in order to guarantee that the retention function is still ensured.

By using forward-osmosis technology in sensitive areas, such as dialysis technology, it is necessary to ensure or at least monitor the correct operation of the FO membrane.

The following can be mentioned as possible solutions:

1. Measuring the resulting osmotic pressure when the FO membrane is operating correctly. If the membrane is in good order, a transmembrane pressure is built up over the FO membrane (the osmotic pressure). The inlets and outlets of the FO filter can be shut off using valves and the osmotic pressure can be measured using a pressure sensor. The filter is accordingly filled in advance (with concentrate on the secondary side and with tap water, for example, on the primary side). The resulting pressure then has to remain constant over a certain time period, otherwise it can be assumed that direct mixing of the liquids normally separated by the FO membrane is taking place.

2. Priming the FO filter by pushing tap water onto the permeate side and then measuring the conductivity of the permeate.

3. Determining the quantities of fluid that have been inlet and removed (at the FO filter) and the conductivity thereof. The plausibility of the dilution by the FO process can then be checked using the values.

4. Filling the filter with air on the secondary side. Admitting liquid on the primary side and measuring the pressure at which the filter is “breached”, i.e. liquid passes over to the secondary side (the bubble-point test).

In accordance with the macro-batch approach, the dialysate generation assisted by forward osmosis takes place as follows:

The solution is produced in one or more batches. The batch may be a bag, for example, which contains the concentrates for producing the solution in a solid or liquid form. It is advantageous for the quantity of dialysate to be sufficient for carrying out dialysis treatment (60 liters to 250 liters).

A description of a possible embodiment of the method is as follows:

Primary Side

The primary side (“feed” side) of the FO membrane is connected to a raw-water source (tap-water connection). The pressure of the raw-water sources or a separate pressure-increasing apparatus (pump or hydrostatic pressure accumulator) ensures that raw water flows over the primary side. The same pressure sources can also be used to initially fill the primary side.

Secondary Side/Secondary Circuit

The secondary side (“product” side) of the FO membrane is connected to the batch, i.e. to the reservoir, preferably to the bag. A separate pressure-increasing apparatus (pump or hydrostatic pressure accumulator) ensures that solution flows over the secondary side.

The solution is preferably repeatedly guided along the FO membrane. That is to say, the batch is connected to the FO filter via a circuit.

Priming (Filling)

At the start, the concentrates are only contained in the batch in dry form or in a slightly diluted form (in the form of a powder, granulate, “slurry” or in liquid form). The concentrates are dissolved/diluted with a little solvent (generally tap water). In this case, the dilution is carried out such that the FO membrane used is not damaged by the still sharply increased electrolyte concentration (no crystallization on the membrane or the like). All the concentrates can be present in the concentrate solution from the start or can only be added to the batch over time.

If the concentrates are only added in a delayed manner, the osmotic pressure gradient can be kept in a range that is optimal for the effectiveness of the FO membrane.

Options for initially diluting/dissolving the concentrates and for priming (filling) the secondary side:

Filter is pre-filled and/or batch is sufficiently pre-filled to start the process and to fill the secondary side/secondary circuit

Priming (filling) the secondary side/secondary circuit by generating negative pressure→pump draws in filtrate on the secondary side and fills the batch bag and the secondary side of the filter (monitoring of the transmembrane pressure by pressure sensor).

Priming (filling) the secondary side/secondary circuit by generating overpressure on the primary side→pressure source pushes filtrate on the primary side and fills the batch bag and the secondary side of the filter (monitoring of the transmembrane pressure by pressure sensor)

Using liquid for priming the filter from the preceding filling process as a priming solution

It is possible to initially only operate/fill the filtrate side using a minimal, i.e. reduced, circuit→reduced secondary volume (suitable small bag shape, FO filter with reduced secondary volume).

Later addition of water, e.g. by volume from FO membrane or through a manual input point on the batch. Aim: Lower priming volume

Production of the Solution

The concentrated solution is conducted past the secondary side of the FO membrane. The high osmotic pressure gradient between the raw water and the solution results in a sustained filtrate flow through the FO membrane into the batch. When a batch is closed, the osmotic pressure gradient decreases and therefore the production of permeate decreases over time. However, a gradient remains until an electrolyte concentration that is typical for a physiological solution is obtained (electrolyte concentration approx. 0.15 mol/L in ready-to-use dialysate).

Stoppage of Production:

Fixed-volume system is filled→target volume is reached/static pressure increases→pressure measured or the process comes to a stop on its own (p_static=p_osmosis)

Shutdown via C (conductivity) or C only protection system

Shutdown via weight determination

Time-controlled

Measuring TMP (transmembrane pressure)/measuring filtrate flow

The process ends once the mixing ratio of A concentrate to permeate is 1:35, for example (=mixing ratio for ready-to-use concentrate).

Tank (fixed volume)

Advantages of the present invention are, in a preferred configuration:

An FO process (in particular FO membranes using Aquaporin technology) uses the osmotic pressure gradient for filtering tap water. The energy-intensive production of permeate is “omitted” and dialysate is directly produced. Nevertheless, comparatively high filtration rates are achieved:

FO filter (e.g. Aquaporin Inside HFFO2): 22.60 liters/m²/hour (25° C./5.8% NaCl solution vs. tap water) RO filter e.g. 50 liters/m²/hour at 15 bar

Since the preparation process takes place immediately before the use of the fluid, i.e. there is no tube network therebetween, the complexity of maintaining the required hygiene is reduced. New options for portability are also conceivable due to continuous miniaturization.

In an FO process, the energy-intensive production of filtrate (permeate) is omitted and physiological solution (dialysate) is directly produced.

The production of permeate via an FO membrane is technically less complex compared with all of said methods (only one FO membrane instead of multiple adsorber cartridges, no tube systems (configured for high pressures)) and is therefore suitable for home systems, as are standard in PD dialysis.

The entire system is therefore compact, cost-saving, less complex, and easier to clean.

In addition, improved filtrate quality can be expected in comparison with adsorber technology, since the retention rates of the FO membranes almost reach the retention rates of RO membranes (RO technology currently produces the maximum retention rate in filtration processes). This is important in the production of hygienically particularly critical PD solutions which are infiltrated directly into a patient's abdomen.

Shipping dry-concentrate bags or highly concentrated concentrates instead of the current ready-to-use liquid solutions (lower transport weight, improved shelf life and sterility)

Overall, the technology is suitable for the decentralized, needs-based production of physiological and hygienic solutions

The process is considerably quieter than an RO system with the associated pump for pressure generation→better suited to the home environment.

FIG. 2 is a schematic view of a device for producing a macro batch:

Reference sign 1 denotes the water connection, reference sign 2 denotes the circulation pump of the mixing circuit, reference sign 3 denotes the FO filter, reference sign 4 denotes the conductivity/temperature measuring cell for raw water and “back-flow” monitoring (could also be arranged between 5 and 2 in the suction line), reference sign 5 denotes the reservoir, preferably bag containing concentrate(s), and reference sign 22 denotes the discharge. As can be seen from FIG. 2 , in this embodiment the first part of the device is not designed as a circuit.

The FO filter is preferably disposable/semi-disposable and is replaced as required (fixed interval, after certain volume of filtrate, “bubble-point test”/“pressure-maintaining test fails”).

The following can be mentioned as options/expansion possibilities:

Air separation in the circuit in order to prevent air at the filter

Pressure increase on the raw-water side in order to increase the flow of raw water or to overlay the FO process with a hydrostatic pressure (→increase in the filtration rate)

Introduction of a physiologically neutral substance to increase the osmotic pressure

Introduction of a substance that can be separated off in a further step (FO agent)—subsequent separation of the agent from the product (as currently standard) e.g. by a thermal process, filtration or by precipitation in the magnetic field (when using a ferrofluid as an agent).

Reuse of dialysate that has already been used, by supplying the used dialysate on the primary side/emptying the bag→drop in weight and volume lower.

Used dialysate is reused during the entire dialysis process

Used dialysate is used at the start of the process (filling secondary circuit)

Monitoring of the transmembrane pressure (limit values specific to FO filter) in order to prevent damage to the FO filter (→important in Aquaporin filters)

FO membrane tests for monitoring the integrity of the filter

Filling/emptying multiple bags simultaneously.

Monitoring the conductivity in the batch, in the suction line upstream of the FO filter or downstream of the FO filter for controlling the filtrate production process

Heater and/or heat exchanger in the primary or secondary circuit (preferably) in order to bring the raw water/filtrate to a temperature that is process-optimized for the FO (25 to 50° C.)

Additional ultrafilter in the supply line upstream of the FO circuit in order to retain high levels of microbiological, chemical or physical contaminants and to therefore reduce the “fouling” of the FO filter and achieve a higher service life

Additional ultrafilter downstream of the FO circuit in order to retain any remaining microbiological (endotoxins), chemical or physical contaminants

Test of the FO filter (e.g. measurement of osmotic pressure) before and after the batch filling, in order to ensure the filter effect and therefore the validity of the batch. Batch only approved after successful test (for example)

In principle, analogous for all described configurations as part of the micro-batch approach

Possible fields of application of the invention are:

Producing HD solution/batch for a treatment e.g. 70 liters

Producing PD solution/batch for a treatment or multiple bags (e.g. 5 liter bags)

Mobile production of NaCl solution (following catastrophes, emergencies or when there is a poor power supply)

Filling genius tank with FO system, producing acute bag 

1. Device for producing dialysate, wherein the device comprises a first part and a second part which is designed as a circuit, wherein the first part comprises a water connection or a water container (2) and the primary side of a filter (4), wherein the filter (4) is designed to produce purified water from the water by forward osmosis, and wherein the second part comprises the secondary side of the filter (4), a reservoir (14), a filtrate line which leads from the secondary side of the filter (4) to the reservoir (14), and a return line (R) leading from the reservoir (14) to the secondary side of the filter (4), wherein an electrodialysis unit (18) comprising a diluate chamber (D) and a concentrate chamber (K1, K2) is further provided, wherein the concentrate chamber (K1, K2) is fluidically connected to the secondary side of the filter (4).
 2. Device according to claim 1, characterized in that the diluate chamber of the electrodialysis unit (18) is fluidically connected to the reservoir (14).
 3. Device according to claim 1, characterized in that a conductivity-measuring cell (16) or a concentration-measuring cell is arranged upstream of the diluate chamber (D) in the flow direction of the dialysate.
 4. Device according to claim 3, characterized in that a pump (13, 24) is arranged between the conductivity-measuring cell (16) or concentration-measuring cell and the electrodialysis unit (18).
 5. Device according to claim 1, characterized in that a conductivity-measuring cell (22) or a concentration-measuring cell is arranged downstream of the diluate chamber (D) in the flow direction of the dialysate.
 6. Device according to claim 1, characterized in that a conductivity-measuring cell (22) or the concentration-measuring cell is arranged between the diluate chamber (D) and the reservoir (14).
 7. Device according to claim 1, characterized in that the conductivity-measuring cell (22) or concentration-measuring cell is arranged between the reservoir (14) and the filter (4).
 8. Device according to claim 7, characterized in that a pump (13) is arranged between the conductivity-measuring cell (22) or concentration-measuring cell and the filter (4).
 9. Device according to claim 1, characterized in that a line portion (L1) is provided which leads from the concentrate chamber to the return line (R).
 10. Device according to claim 1, characterized in that dialysate concentrate is contained in the reservoir (14).
 11. Device according to claim 1, characterized in that a plurality of reservoirs (14) are provided and in that a valve assembly is provided which is designed to alternately switch a plurality of reservoirs into a fluidic connection to the second part of the device.
 12. Device according to claim 1, characterized in that a bicarbonate concentrate and/or an acidic concentrate which is configured to produce dialysate is contained in the reservoir (14).
 13. Device according to claim 1, characterized in that a plurality of compartments are provided in the reservoir (14), in each of which one or more concentrates are contained.
 14. Device according to claim 1, characterized in that the concentrate is contained in the reservoir (14) in the form of a powder, granulate, slurry or in liquid form.
 15. Method for producing dialysate using a device according to claim 1, characterized in that water is supplied to the primary side of the filter (4), in that the permeate is supplied to the secondary side by forward osmosis, and in that a dialysate concentrate that is mixed with the permeate is supplied to the secondary side of the filter (4) from the reservoir (14) and/or from another source, and in that the concentration of the dialysate is increased on the secondary side by electrodialysis.
 16. Method according to claim 15, characterized in that the dialysate or dialysate concentrate is conveyed in the circuit on the secondary side of the filter (4) until the conductivity and/or a concentration or another parameter representative of these parameters corresponds to a target value or is in a target-value range.
 17. Method according to claim 15, characterized in that a plurality of reservoirs (14) are provided in the second part of the device, one reservoir (14) being filled with the dialysate or the dialysate concentrate and the other reservoir (14) being emptied for use in a dialysis machine.
 18. Method according to claim 15, characterized in that a physiologically acceptable substance, in particular glucose, or a substance that is to be precipitated before use as dialysate, in particular magnetic iron nanoparticles, is added in order to increase the osmotic pressure on the secondary side of the filter (4). 